how close would be too close for these plants to be?* There's not much I want to plant, but I do have tomatoes, and am going to plant some sweet potatoes too.* would opposites of the same 6ft bed still be too close?* I can find somewhere else for the berries, it's just not as great a spot for them, though there's really no other place for the rest of the garden.
Also avoid planting where any nightshade family members - tomatoes, potatoes, eggplants, peppers - grew in the last 2 years, as they can transmit verticillium wilt to blackberry plants.